ERC-404

ERC-404 originated with Pandora as an experiment for giving NFT collections native liquidity and fractional ownership. A contract maintains two coordinated representations: fungible units and complete NFTs. When an account gains or loses enough units, the system mints, transfers or burns the linked NFT according to the implementation rules.

The name can be misleading: ERC-404 is not a final standard in the EIP/ERC process. Its official repository describes version 2 as beta, experimental and unaudited, so it should not be presented as a stable interface or assumed compatible with every wallet, marketplace or DeFi protocol. Integrations should review rounding effects, transfer exemptions and emitted events in particular.

For dual-nature token designs with a formal specification, the current reference is ERC-7631, which defines the relationship between a base ERC-20 contract and an ERC-721 mirror contract without retroactively turning ERC-404 into a standard.